Solicitor Michael Lynn told a judge that he was unaware of 33 arrest warrants issued by a Dublin court until the day he was arrested at his bolthole in Brazil.
Mr Lynn has been pursued by the Irish authorities for six years in relation to an alleged €80m mortgage fraud. He fled first to Portugal, then to Brazil.
But at a hearing at the Federal Court in Pernambuco, he told Judge Flávia Tavares Dantas he was unaware of the warrants until his arrest on August 28.
Instead, he said, his reason for moving to Brazil was that he wanted to start a business in a country that was having "economic success".
The exchanges – in which Mr Lynn is also said to have been told to "shut up" by the judge after interrupting her – emerged on Wednesday in a statement from a court spokesman.
Mr Lynn had arrived at the court – his first trip outside the grim, high-security Cotel jail in the Brazilian city of Recife, for seven weeks in a small cell – in the boot of a blacked out 4x4, with its red lights flashing.
During the hearing, attended by representatives of the Irish Government, Mr Lynn's lawyers and wife, federal prosecutors and an interpreter, Lynn invoked his right to silence against the charges.
A court spokesman said: "He explained to the court that he had arrived in Brazil in June 2011, first living in Sao Paulo. He then moved to Pernambuco in May 2012, working as an English teacher. "He told the court he wanted to open a business here as it was a country with 'economic success'."
"When asked whether he knew of 33 arrest warrants issued by the Dublin Metropolitan District Court, Lynn said he only became aware of them on the day of his arrest."
A video of the testimony will now be sent to the Supreme Court in the capital Brasilia. Lynn's lawyers now have 10 days to file a defence before a panel of judges decides his fate.
There is said to be no deadline for the final decision on Ireland's extradition request. While there is no extradition treaty between the two countries, there is a temporary bilateral agreement.
Mr Lynn arrived at the hearing in handcuffs, but during the testimony he was allowed to remove them.
At the request of Mr Lynn, his defence lawyers declined to comment to the press.
Lynn was arrested near his Recife beach villa two months ago. He lived openly in Brazil with his wife, teaching English at a local school run by a British expat, enjoying a local country club and starting his own property business.